Widespread acceptance of the CT scanner has focused attention on the potentials for development of new technologies in imaging. In the years since the introduction of the CT imaging method, innovative technological improvements have been rapid. Imaging research has reached a point at which it is imperative that the radiological and scientific communities assess its current status. The American College of Radiology, a non-profit educational and scientific organization, proposes an expository conference which will be primarily concerned with five emerging modalities of potentially great significance. The five modalities selected for review by the ACR Committee on Emergent Imaging Modalities are (1) new developments in ultrasound; (2) electronic recording and processing of radiological images; (3) transmission computed tomography; (4) positron emission tomography; and (5) nuclear magnetic resonance imaging. The objectives of the proposed conference are to assess current imaging research in these five areas to determine their potential usefulness; to identify avenues of new research; and to anticipate problems associated with their introduction into the clinical setting. Research radiologists, imaging scientists, industrial scientists, and representatives from federal agencies concerned with imaging technology will be invited. The conference method to be employed will provide for an active exchange of ideas between the speakers and participants. The discussion will be recorded and made available to the radiological and scientific communities. Some 15 to 20 radiological and physical scientists will be invited to make presentations on the selected modalities. Speakers competent in health technology development and health economics will also be invited to talk about the impact of new imaging modalities on health planning and health economics.